The last cutscene in the game is an hour I believe. Really good game though. I think it was my first PS3 game ever.

Is Ground Zeroes the one they were hyping up last year? Why is it so cheap?

It's cheap cause it's a short game. It's a prologue to the much bigger Metal Gear Solid V Phantom Pain releasing in about a year. Gameplay is anywhere from 2 hours to 10 depending on how you wanna play it.